1. Technical Field
The present invention relates to a metal golf club shaft, to a method of producing the golf club shaft, and to a golf club with the golf club shaft.
2. Background Art
As a technique for improving the design of a metal golf club shaft, a technique of coating the surface of a shaft is known (for example, see Japanese Patent Application Laid-Open No. 2002-362099).
In general, when a coating is directly applied to a metal golf club shaft, adequate coating strength may be obtained, but rusting may occur at areas at which the coating peels off. This rusting may cause damage to the shaft if the corrosion expands from such areas, and therefore, rusting is undesirable.
As a technique for preventing generation of corrosion, a method of forming a plated layer and further coating the plated layer may be mentioned, and the plated layer functions as a corrosion-resistant layer. A plated layer obtained by forming a nickel layer and forming a chrome layer thereon is effective as the plated layer. The nickel layer increases adhesion of the chrome layer with respect to the surface of the base metal shaft, and the nickel layer has sealing characteristics for preventing moisture from penetrating to the base metal shaft. The chrome layer functions as a hard layer for protecting the surface and also functions as a layer exhibiting a metallic luster.
According to this structure, even when the coating peels off, rusting can be prevented due to the plated layer. In addition, a scratch-resistant surface is obtained, and a metallic luster is obtained. However, when coating is applied after a plated layer is formed, the coating strength is low, and the coating may easily peel off.
As a method for improving the coating strength, the following method may be used. In this method, after a plated layer is formed, the surface of the plated layer is ground so as to roughen the surface, thereby improving adhesion of the coating. In this case, the coating strength is improved compared to that in a case in which grinding is not performed, but the degree of coating strength is insufficient for the degree of coating strength required for golf club shafts.